The fuel gas derived from coal gasification contains gaseous species such as CO/CO2, H2/H2O and CH4, as well as gaseous compounds of sulphur, nitrogen and chlorine and entrained solids of char and ash. On exiting the gasifier vessel temperatures can be between 673K and 1273K with a pO2 as low as 10-25 atm. and pS2 as high as 10-7 atm. making the environment extremely reducing and sulphidising. In this area, high temperature particle control filters are required to meet environmental and turbine equipment requirements. The aim of this research was to evaluate the effect of a simulated gasification atmosphere on the mechanical properties of a clay-bonded SiC by considering the thermodynamic stability of the possible gas and solid chemical reactions. Temperatures between 873K and 1273K were employed for up to 200 hours with 3- point bend tests used to measure changes in strength. Three atmospheres (A, B and C) were employed to investigate the effects of sulphur, water vapour and chlorine respectively. Analytical techniques (e.g. SEM, XRD and EDX) coupled with complex thermodynamic calculations allowed the investigation of the corrosion mechanisms for these materials under simulated gasification conditions. It was found that a severe strength degradation of the filter material occurred due to volatilisation of clay-binder constituents and this volatilisation was accelerated by the addition of water vapour. Micro-crack formation due to stresses induced by devitrification and cooling also severely reduced the room temperature fracture strength.

Subject
Materials, Mass loss, Binders, Silicon carbide, Carbon monoxide, Surfaces, Gasification, Filters, Sodium, Gases, Risk reduction, Fracture, Chemical reactions
Keywords:
coal gasification, reducing atmosphere, hydrolysis, chlorination, sulphidation corrosion, silicon carbide, filters, strength
© 1998 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1998
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.